This invention relates to honeycomb articles and more particularly to honeycomb articles for providing mixing of one or more workstreams between individual channels of the honeycomb by using grooved areas to segment the individual channels and serve as mixing sites to thermally equilibrate, physically mix, or chemically react the various workstreams.
Honeycomb articles have been well documented in the patent literature. They can be used in a number of very useful applications involving their chemical, physico-chemical, physical, and mechanical properties. These include such diverse uses as purification, filtration, chemical reaction vessels, photonic band gap structures, microlens arrays, high temperature dielectric materials and even lightweight structural supports. They have been found exceptionally useful as components of catalytic converters for vehicles operating with internal combustion engines.
Because of their structure, honeycomb articles have a high surface area along with low pressure drop. This combination can be used advantageously in some applications, especially compared to applications that use packed bed columns. In these cases, the honeycomb article may not be merely an inert feature in the process, but rather may be a dynamic participant, involved either by utilizing the chemical composition of its channel walls to react with a workstream or its ability to adsorb specific materials from the workstream. These properties can be modified by temperature control or by designing the honeycomb with a specific composition such as glass, ceramic, metal, or graphite or by adjusting the porosity of the channel surfaces and walls. Further modifications can be achieved by coating the surface of the honeycomb channels with reactive, catalytic or adsorptive materials. This great amount of flexibility of design and fairly simple manufacture has made honeycomb structures commonplace in such diverse areas as fluid separations and catalytic converters.
Despite the many advantages and uses for honeycomb articles, these structures have some characteristics that are disadvantageous for certain applications. One such characteristic is that the individualized channels, even with good porosity, do not provide good mixing among workstreams in adjacent channels. For the purpose of this patent, workstreams are defined as feedstock fluids such as a gas or liquid to which either a chemical or physical change is desired. This segregated channel flow of honeycombs is not disadvantageous in certain applications where a single workstream is being processed in an isothermal environment. In other cases, however, the lack of either thermal or physical mixing can lead to inefficiencies or, in worst cases, complete failure of a desired process.
The requirement for good mixing and thermal equilibrium has led to designs that are related to honeycomb structures but allow for intermixing between channels. These structures are invariably complex and correspondingly more difficult to manufacture. To fabricate such structures by extrusion, movable dies are generally required. There is significant difficulty cleaning moveable die equipment and maintaining a continuous operation, free from downtime. Examples of such mixing articles and processes for making such articles can be found in U.S. Pat. No. 5,032,156 to Luder et al., U.S. Pat. No. 5,240,663 to Stringaro et al., U.S. Pat. No. 5,928,521 to Levec, U.S. Pat. No. 5,525,291 to St. Julien, and European Patent Application EP 0,705,962A to Toyao et al.
Therefore there exists a need to provide an economic structure that will allow facile chemical and/or thermal mixing of various workstreams. Another need is to provide a structure that allows for good mixing and intimate contact of workstreams from countercurrent flow. Still another need is to develop a structure for mixing or use as a substrate for active catalysts, adsorbers, etc. that will provide the ability to process great quantities of fluids without experiencing a great pressure drop, yet be easily manufactured.